Spike fitted on a vehicle tire for perpendicular contact with the road

ABSTRACT

The present invention concerns a fixed spike, or a sleeve-mounted spike, fitted on a vehicle tire. The fixed spike or the sleeve-mounted spike, features an asymmetric region which is disposed to produce a force component (F 2 ) turning the fixed spike, or the sleeve-mounted spike (20) so that the fixed spike, or the sleeve-mounted spike (20) is arranged, at initial contact with the road surface (17), to meet the road surface (17) substantially in vertical position.

BACKGROUND OF THE INVENTION

The present invention concerns a fixed spike on a sleevemounted spike,fitted on a vehicle tyre.

Increasing traffice load and spike tyres in combination have proven tobe a remarkable road attrition factor. In some countries this has evenled to prohibition of spike tyres, or at least to considerablerestrictions.

In Nordic conditions, the beneficial effect of anti-slip means on thesafety and flexibility of traffice has on the other hand beenirrefutably demonstrated, and this effect should not be sacrificed:instead, the associated drawbcks should be eliminated. Good results willbe achieved by further developing both the road superstructures and theanti-slip tyres.

As a pneumatic automobile tyre rolls on an even surface, it isconsiderably flattened radially, owing to its flexibility, whereby inthe contact region longitudinal as well as transversal forces aregenerated owing to changes of the rolling radius.

The longitudinal forces acting on the spike when the tyre is rolling aredue to bending of the body structure, to longitudinal slipping and tothe stress wave in the rubber.

When a spike approaches the point of contact with the road, the tyrebody undergoes bending such that the radius of the bent part issignifically smaller than that of equivalent parts of the load-freetyre. This deflects the spike, which has been mounted at right anglesagainst the surface, to assume a vertical position before contact withthe road. Owing to the protrusion of the spike point, however, the spikeis not turned into sufficiently upright position: it meets the roadsurface in an oblique position. At this stage, he forces due to slippingtendency also begin to exert their influence. As the rotating tyresurface and the protruding body (the spike) attached thereto meet theroad surface, a dynamically caused impact against the road surface isproduced. The attrition of the road can be significally reduced if saidimpact can be eliminated or reduced.

The impact has been found to be due to the kinetic energy of the spike,in other words, due to the mass of the spike and its velocity in thedirection against the road surface. The effective mass is influenced bythe spike mass itself and, in addition, by a friction force, itsmagnitude depending, in its turn, on the spike design in that thefriction of a spike body mounted in a sleeve results from slidingbetween the sleeve and the metallic body, while the friction force of afixed spike is active between the spike body and the rubber. The mass ofa fixed spike is influenced, owing to its shaping, partly also by themass of the surrounding rubber.

Prior designs have not eliminated the abrasion effect from the dynamicimpact in any other way than by reducing the mass of the spike, and itis believed that the practical minimum limit has already been reached inthis respect. As taught by the new invention, certain design featuresare suggested for the spike and the tyre with the express aim to reducethe dynamic initial contact peak and the ultimate scratch.

Traditionally, the shape of the spike has been symmetric and it has beenmounted in a hole, perpendiculalr against the wear surface of the tyre,whereby it meets the road in a slightly oblique position as the forcesmentioned affect its position. The oblique contact of the spike with theroad, as well as its being pushed deeper into the tyre in obliqueposition during the initial part of road contact, cause damage to therubber and to the spike which impairs the friction properties of thespike, detracts from the durability of the spike and increases its roadattrition properties.

SUMMARY OF THE INVENTION

The aim of the invention is to achieve an improvement in currently knownfixed spike designs on sleeve-mounted spike designs. The more specificaim of the invention is to provide a fixed spike, on a sleeve-mountedspike, in which the drawbacks troubling designs of prior art have beenavoided.

The aims of the invention are achieved by means of a fixed spike, on asleeve-mounted spike, which is mainly characterized in that the fixedspike, on the sleeve-mounted spike features an asymmetric region whichhas been disposed to produce a force component turning the fixed spikeon the sleeve mounted spike, in such manner that the fixed spike, on thesleeve-mounted spike has been arranged to meet the road surface, atinitial contact with the road surface, in a position which issubstantially perpendicular. Accordingly, the present invention isdirected to a fixed spike or a sleeve-mounted spike, fitted on a vehicletire, characterized in that the fixed or sleeve-mounted spike has anasymmetric region disposed to produce a force component (F₂) turning thefixed spike (10) or the sleeve-mounted spike (20) so that the fixedspike (10) or the sleeve-mounted spike (20) is arranged, at initialcontact with the road surface (17), to meet the road surface (17) in asubstantially perpendicular position.

Other characteristic features of the fixed spike, on sleeve-mountedspike of the invention are presented below.

As taught by the invention, the dynamic impact force is reduced byexerting an effect on the spike just before the onset of road contact inthat its movement is stopped by directing a lifting force componentthereon. In addition, the road contact is made less abrasive on the roadwhen the spike is lifted to a more nearly vertical position in relationto the road surface; the more upright position of the spike also reducesthe scratching wear in the terminal part of the road contact area andincreases the durability of the spike in the tyre.

When an asymmetric spike is mounted in a conventional spike hole, itbecomes already positioned at installation so that its road contact willtake place with the spike in a position which is substantially moreupright against the road surface than that of an equivalen symmetricspike. By designing the configuration of the asymmetric beak and of theregion generating the counterforce, and by the extent to which the spikeprojects, the position of the spike at the moment immediately beforeroad contact is adjusted to be optimal.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in the following in more detail by referringto some advantageous embodiments of the invention, presented in thefigures of the drawing attached, yet to which the invention is not meantto be exclusively confined.

FIG. 1 presents an advantageous embodiment of the fixed spike of theinvention; and

FIG. 2 presents an advantageous embodiment of the sleeve-mounted spikeof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 the fixed spike of the invention in general is indicated byreference numeral 10. The fixed spike 10 is composed of a body part 11,a flange part 12 and a point 13. The rubber of the vehicle tyre isindicated by reference numeral 14, and the wear surface of the tyre byreference numeral 16.

As described by the basic idea of the invention, the fixed spike 10 ismade asymmetric. In the present embodiment, asymmetry has beenimplemented by designing the flange 12 to be asymmetric on one maragin15. The asymmetric part 15 need not necessarily occur on the flange 12:a similar asymmetric part 15 may also be provided on the body part 11.In the most advantageous embodiment, the asymmetric part 15 constitutesa kind of beak disposed to take up the resultant of the road contactforce, indicated in FIG. 1 by arrows R_(O) --R₂. In FIG. 1, the drivingdirection is indicated by arrow A and the road surface, by referencenumeral 17.

In the embodiment of FIG. 2, the sleeve-mounted spike of the inventionin general is indicated by reference numeral 20. The sleeve-mountedspike 20 has a rivet 21, a flange 22 on the rivet 21, a point 23 and asleeve 24. The protrusion of the spike from the wear surface 16 isindicated by e.

As taught by the basic idea of the invention, the sleeve 24 is providedwith an asymmetric region 25 disposed to take up the resultant R_(O)--R₂ of the road contact force in a way similar to that in theembodiment of FIG. 1. In this embodiment, the asymmetric region isprovided on the sleeve at a height which is substantially consistentwith the location of the flange 22 of the ribet 21. The asymmetricregion 25 is a claw-like region. The asymmetric region 25 may, ofcourse, equally be located slightly higher on the sleeve (i.e. deeperinto the tire rubber 14, thata is, similarly as in the embodiment ofFIG. 1, in other words, in the sleeve region at the height correspondingto the upper part of the rivet 21. The other reference numeralscorrespond to those in the embodiment of FIG. 1.

When the spike of the invention is installed in the hole, the spikecauses a static stress region in the surrounding rubber. When the stresswave caused by compression of the tyre meets the stress region of thesppike asymmetrically, and exceeds it, the spike turns owing to thecompressed state of the rubber. At the same time, the spike isinfluenced by forces arising from the rotation of the tyre. Thesituation is illustrated by FIGS. 1 and 2.

In a static situaation and at low speeds, the pressure effectoriginating from the contact angle K of the rubber is uniform and itsresultant R_(O) is very closes to vertical. The rear margin of therubber pieces bulges out rearwardly and the contact surface, 16forwardly against the road 17. With higher spped, the pressure resultantturns forward in the direction R₁, and the pressure pattern becomes morepronouncedly oval. The pressure resultant is also turned forward becausein the region B the pressure in the rubber is lower since no compressionforce is present there. Owing to the rotation of the tyre and thecompression of the rubber, the pressure resultant also moves forward tothe point R₂, whereby it encounters the spike flange and impaarts to itan upward acceleration, with the component F₁, and at the same timeturns it from the position as installed to a position more nearlyperpendicular against the road surfce, with the component F₂. The spikeis enabled to turn because there is no compression forward of it. It ispossible to influence the utilization of said forces by the mode ofinstalling the spike and by its shape features. A shaped structure alsocreates on the side where said pressure resultants act, a wider localpressure region on which the pressure resultant from the compressedrubber exerts an even more powerful effect. In other words, theasymmetric region 15, 25 is at the same time disposed to produce a forcecomponent F₁ lifting the fixed spike 10 or the sleeve-mounted spike 20,whereby the velocity, due to rotation of the tire, at which the spikeand the road meet has at the same time been arranged to be substantiallyreduced.

I claim:
 1. A spike fitted on a vehicle tire comprising a hole for saidspike substantially perpendicular to a wear surface,said spikecomprising an asymmetric region positioned thereon to cause a staticstress region in surrounding rubber of said tire which, when a stresswave caused by compression of said tire rubber meets said asymmetricstatic stress region, generates a force component (F₂) during tirerotation upon driving which acts to turn said spike to a positionsubstantially perpendicular to a surface on which the tire is beingdriven, whereby said spike is oriented prior to initial contact with thesurface, to meet the surface at said initial contact in saidsubstantially perpendicular position.
 2. The spike of claim 1, which isa fixed spike.
 3. The spike of claim 1, wherein said spike is asleeve-mounted spike.
 4. The spike of claim 2, additionally comprisingaflange thereon which comprises at least part of said asymmetric region.5. The spike of claim 2, additionally comprising a body portion thereof,said body portion comprising at least part of said asymmetric region. 6.The spike of claim 3, additionally comprising a sleeve, a rivet mountedin said sleeve, and a flange on said rivet,with said sleeve comprisingsaid asymmetric region at a location corresponding to said flange ofsaid rivet.
 7. The spike of claim 3, additionally comprising a sleeve, arivet mounted in said sleeve, and a flange on said rivet,with saidsleeve comprising said asymmetric region at a location substantially atan area of an upper part of said rivet.
 8. The spike of claim 9, whereinsaid asymmetric region is additionally positioned to generate a forcecomponent (F₁) lifting said spike,whereby velocity, due to rotation ofthe tire, at which said spike and the surface meet, is substantiallyreduced.
 9. The spike of claim 2, additionally comprising, in thefollowing order, a flange, a body portion, and a point for protruding inthe tire,with said body portion comprising said asymmetric region.